/*
 * Created on Oct 08, 2004
 * Created by Alon Rohter
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */
package com.aelitis.azureus.core.util.average;

/**
 * Implements a basic moving average.
 */
public class MovingAverage implements Average {

    private final int periods;
    private double data[];
    private int pos = 0;
    private double total;

    /**
     * Create a new moving average.
     */
    public MovingAverage(int periods) {
        this.periods = periods;
        reset();
    }

    public void reset() {
        pos = 0;
        total = 0;
        data = new double[periods];
    }

    /**
     * Update average and return average-so-far.
     */
    public double update(final double newValue) {
        total -= data[pos];
        total += newValue;

        data[pos] = newValue;
        pos++;
        if (pos == periods)
            pos = 0;
        return calculateAve();
    }

    /**
     * Return average-so-far.
     */
    public double getAverage() {
        return calculateAve();
    }

    private double calculateAve() {
        if (pos == 0) {
            // resync (I'd prefer not to do this but just in case)
            double sum = 0.0;
            for (int i = 0; i < periods; i++) {
                sum += data[i];
            }
            total = sum;
        }

        return total / periods;
    }
}
